1. Technical Field of the Invention
The present invention relates to a tuning-fork-type piezoelectric resonator element and a tuning-fork-type piezoelectric resonator, and more particularly to a tuning-fork-type piezoelectric resonator element and a tuning-fork-type piezoelectric resonator, which are suitable for miniaturizing and thinning a tuning-fork-type piezoelectric resonator.
2. Description of the Related Art
A piezoelectric resonator, particularly, a tuning-fork-type piezoelectric resonator is known as a piezoelectric resonator that can obtain an accurate clock frequency simply and easily. Recent demands to miniaturize and thin electronic devices require a tuning-fork-type piezoelectric resonator to be miniaturized and thinned. To meet such a demand, a surface mounting type tuning-fork-type piezoelectric resonator has been developed. The tuning fork piezoelectric resonator of this surface mounting type is mounted so that the surface of a tuning-fork-type piezoelectric resonator element is made parallel to the bottom face of a package, and the tuning-fork-type piezoelectric resonator element is mounted at the bottom face of the package in the form of a cantilever.
Further, the technique of mounting a tuning-fork-type piezoelectric resonator in a package is disclosed in Japanese Unexamined Patent Application Publication No. 2001-332952. In Japanese Unexamined Patent Application Publication No. 2001-332952, the tuning-fork-type piezoelectric resonator element is mounted in the package including a package base and a cover in the form of a cantilever. Also, a concave portion having a rectangular shape in a plan view is provided at the package base adjacent to resonating arms of the tuning-fork-type piezoelectric resonator element. The provision of the concave portion allows a free end of the tuning-fork-type piezoelectric resonator element to enter the package base without contact therewith, even though the resonator element vibrates greatly due to an external shock. As a result, the tuning-fork-type piezoelectric resonator element is not deformed and the frequency characteristics are prevented from being changed.
In addition, another mounting method includes the technology disclosed in Japanese Unexamined Patent Application Publication No. 56-61820. In Japanese Unexamined Patent Application Publication No. 56-61820, a frame is provided at a tuning-fork-type piezoelectric resonator element to surround a tuning-fork-type piezoelectric resonator body. The tuning-fork-type piezoelectric resonator element is interposed between two packages, which are joined to each other and sealed by metal material. At this time, the joining and sealing are made with the frame protruding farther than the package. The protruding part of the frame functions to prevent the metal material provided at upper and lower sides of the frame from being short-circuited.
Meanwhile, in the conventional tuning-fork-type piezoelectric resonator, the tuning-fork-type piezoelectric resonator element is mounted via a base in the form of a cantilever. However, since the tuning-fork-type piezoelectric resonator element is mounted on the base in the form of a cantilever, the parallelism of the tuning-fork-type piezoelectric resonator element mounted inside the package becomes lowered, and the tuning-fork-type piezoelectric resonator element is slantingly mounted therein. Therefore, the conventional tuning-fork-type piezoelectric resonator has a problem in that the resonating arms may come in contact with the bottom face of the package or the cover, thereby stopping oscillation.
Moreover, in the conventional tuning-fork-type piezoelectric resonator described in Japanese Unexamined Patent Application Publication No. 2001-332952, in order to prevent the resonating arms from contacting with the bottom face of the package, a concave portion is formed at the bottom face of the package. The concave portion should have enough depth to reliably prevent the contact of the resonating arms with the package, and thinning the tuning-fork-type piezoelectric resonator becomes difficult. Furthermore, a base on which the resonating arms of the tuning-fork-type piezoelectric resonator protrude is mounted on the package base, causing the problem of increasing vibrating leakage and a crystal impedance (CI) value.
Furthermore, in the conventional tuning-fork-type piezoelectric resonator described in Japanese Unexamined Patent Application Publication No. 56-61820, when two electrodes of the tuning-fork-type piezoelectric resonator element and a package-side mounting electrode are electrically connected to one another by a conductive adhesive, the two electrodes of the tuning-fork-type piezoelectric resonator element and the package-side mounting electrode approach each other. Thus, the conductive adhesive may overflow, causing short-circuiting between the electrodes.
The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a tuning-fork-type piezoelectric resonator element capable of being mounted in a package while keeping the parallelism thereof. It is another object of the present invention to provide a tuning-fork-type piezoelectric resonator that can be thinned using the tuning-fork-type piezoelectric resonator element.